Notice how often your mind is somewhere else. Rehearsing a conversation that has not happened. Replaying one that has. Imagining what someone thinks of you. Planning a life you are not living.

This is daydreaming, and the tradition calls it fantasy. It runs on its own, it uses a great deal of energy, and it keeps us asleep. A day can produce a thousand inner pictures and leave you more tired than if you had worked.

But the faculty doing it is precious. Imagination is how you picture a loved one’s face, how an artist sees a painting before it exists, how a person finds a way out of a problem. The books describe two kinds. One is mechanical: it drifts, mostly into fears and wants. The other is conscious: you choose what to picture, and hold it there.

The work is not to stop imagining. It is to take your imagination back. Later pages teach you to use it on purpose, in meditation and at night. For now, start by noticing where it goes when no one is steering.

A daydream usually begins at a certain moment: when something is boring, uncomfortable or sad. It is often a way of leaving.